1. Field of Invention
This invention relates to a shutter for use in a physical vapour deposition apparatus having a chamber.
2. Description of Related Art
It is well known in physical vapour deposition chambers, such as sputter deposition chambers, to line the walls with shielding to capture any unwanted deposition. The shielding is generally retained in place by a combination of physical fit and gravity and, since most shielding is not required to move during the process, this works perfectly well.
For a number of processes, for instance reactive sputter deposition, there is a shielding component, called the process shutter, which must be able to move. The process shutter is provided to cover the substrate support pedestal for example during the target clean-up process, which is carried out between successive substrate deposition processes. During the actual deposition process, the shutter must be located in some part of the chamber, where it will not compromise the uniformity of deposition of the substrate. In some chambers the shutter is translated in a horizontal plane (by rotary or linear action) so that it lies within an adjacent pocket or housing. In others, it is rotated into a space beneath or beside the support pedestal.
Because, during use, the shutter receives deposition, it must (in whole or in part) be easily removable, so that it may be replaced at appropriate intervals by a clean component. Another design constraint is that the shutter movement must be as rapid as possible and this generally requires that the shutter be rigidly attached to its actuating mechanism. Commonly this is achieved by bolting the two parts together.
Since, for most chambers, maintenance access is generally from above, by means of removal of the target, it is convenient if the fixing screws are located in the upper surface of the shutter. However, in this position, they generally receive a significant amount of deposited material and can be extremely difficult or impossible to remove subsequently. In addition, the sharp features associated with the screw head may cause local delamination of the deposited film, resulting in particulate contamination of the substrates processed within the chamber.
In order to overcome these limitations, fixing screws are commonly located in positions away from the primary deposition flux. However, this immediately makes the removal of the screws more difficult, because maintenance access is much less straight forward.